Efficient Hash Probes on Modern Processors
Kenneth Ross (Columbia University)
Friday, February 2, 2007
11am
EBII 3211 — NCSU Centennial Campus
(Driving directions and parking suggestions)
Bucketized versions of Cuckoo hashing can achieve 95– 99% occupancy, without any space overhead for pointers or other structures. However, such methods typically need to consult multiple hash buckets per probe, and have therefore been seen as having worse probe performance than conventional techniques for large tables. We consider workloads typical of database and stream processing, in which keys and payloads are small, and in which a large number of probes are processed in bulk. We show how to improve probe performance by (a) eliminating branch instructions from the probe code, enabling better scheduling and latency-hiding by modern processors, and (b) using SIMD instructions to process multiple keys/payloads in parallel. We show that on modern architectures, probes to a bucketized Cuckoo hash table can be processed much faster than conventional hash table probes, for both small and large memory-resident tables. On a Pentium 4, a probe is two to four times faster, while on the Cell SPE processor a probe is ten times faster.
About the speaker: Kenneth Ross is a Professor in the Computer Science Department at Columbia University in New York City. His research interests touch on various aspects of database systems, including query processing, query language design, data warehousing, and architecture-sensitive database system design. Professor Ross received his PhD from Stanford University. He has received several awards, including a Packard Foundation Fellowship, a Sloan Foundation Fellowship, and an NSF Young Investigator award.
The talk is sponsored by Dr. Michael Rappa and the Initiative for Advanced Analytics
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